/*******************************************************************************
 * Copyright 2011 See AUTHORS file.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ******************************************************************************/
package com.badlogic.gdx.utils;

import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.CharBuffer;
import java.nio.DoubleBuffer;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;
import java.nio.LongBuffer;
import java.nio.ShortBuffer;

/**
 * Class with static helper methods to increase the speed of array/direct buffer and direct buffer/direct buffer transfers
 * 
 * @author mzechner
 * 
 */
public class BufferUtils {
	/**
	 * Frees the memory allocated for the ByteBuffer. DO NOT USE THIS ON BYTEBUFFERS ALLOCATEd
	 * VIA METHODS IN THIS CLASS OR ByteBuffer.allocateDirect()! IT WILL EXPLODE!
	 */
	public static native void freeMemory(ByteBuffer buffer) /*-{ }-*/;
	
	/**
	 * Copies numFloats floats from src starting at offset to dst. Dst is assumed to be a direct {@link Buffer}. The method will
	 * crash if that is not the case. The position and limit of the buffer are ignored, the copy is placed at position 0 in the
	 * buffer. After the copying process the position of the buffer is set to 0 and its limit is set to numFloats * 4 if it is a
	 * ByteBuffer and numFloats if it is a FloatBuffer. In case the Buffer is neither a ByteBuffer nor a FloatBuffer the limit is
	 * not set. This is an expert method, use at your own risk.
	 * 
	 * @param src the source array
	 * @param dst the destination buffer, has to be a direct Buffer
	 * @param numFloats the number of floats to copy
	 * @param offset the offset in src to start copying from
	 */
	public static void copy (float[] src, Buffer dst, int numFloats, int offset) {
		copyJni(src, dst, numFloats, offset);
		dst.position(0);

		if (dst instanceof ByteBuffer)
			dst.limit(numFloats << 2);
		else if (dst instanceof FloatBuffer) dst.limit(numFloats);
	}
	
	/**
	 * Copies the contents of src to dst, starting from src[srcOffset], copying numElements
	 * elements. The {@link Buffer} instance's {@link Buffer#position()} is used to define
	 * the offset into the Buffer itself. The position will stay the same, the limit will be
	 * set to position + numElements. <b>The Buffer must be a direct Buffer with native byte order.
	 * No error checking is performed</b>.
	 * 
	 * @param src the source array.
	 * @param srcOffset the offset into the source array.
	 * @param dst the destination Buffer, its position is used as an offset.
	 * @param numElements the number of elements to copy.
	 */
	public static void copy (byte[] src, int srcOffset, Buffer dst, int numElements) {		
		copyJni(src, srcOffset, dst, positionInBytes(dst), numElements);
		dst.limit(dst.position() + bytesToElements(dst, numElements));
	}
	
	/**
	 * Copies the contents of src to dst, starting from src[srcOffset], copying numElements
	 * elements. The {@link Buffer} instance's {@link Buffer#position()} is used to define
	 * the offset into the Buffer itself. The position will stay the same, the limit will be
	 * set to position + numElements. <b>The Buffer must be a direct Buffer with native byte order.
	 * No error checking is performed</b>.
	 * 
	 * @param src the source array.
	 * @param srcOffset the offset into the source array.
	 * @param dst the destination Buffer, its position is used as an offset.
	 * @param numElements the number of elements to copy.
	 */
	public static void copy (short[] src, int srcOffset, Buffer dst, int numElements) {		
		copyJni(src, srcOffset << 1, dst, positionInBytes(dst), numElements << 1);
		dst.limit(dst.position() + bytesToElements(dst, numElements << 1));
	}
	
	/**
	 * Copies the contents of src to dst, starting from src[srcOffset], copying numElements
	 * elements. The {@link Buffer} instance's {@link Buffer#position()} is used to define
	 * the offset into the Buffer itself. The position will stay the same, the limit will be
	 * set to position + numElements. <b>The Buffer must be a direct Buffer with native byte order.
	 * No error checking is performed</b>.
	 * 
	 * @param src the source array.
	 * @param srcOffset the offset into the source array.
	 * @param dst the destination Buffer, its position is used as an offset.
	 * @param numElements the number of elements to copy.
	 */
	public static void copy (char[] src, int srcOffset, Buffer dst, int numElements) {		
		copyJni(src, srcOffset << 1, dst, positionInBytes(dst), numElements << 1);
		dst.limit(dst.position() + bytesToElements(dst, numElements << 1));
	}
	
	/**
	 * Copies the contents of src to dst, starting from src[srcOffset], copying numElements
	 * elements. The {@link Buffer} instance's {@link Buffer#position()} is used to define
	 * the offset into the Buffer itself. The position will stay the same, the limit will be
	 * set to position + numElements. <b>The Buffer must be a direct Buffer with native byte order.
	 * No error checking is performed</b>.
	 * 
	 * @param src the source array.
	 * @param srcOffset the offset into the source array.
	 * @param dst the destination Buffer, its position is used as an offset.
	 * @param numElements the number of elements to copy.
	 */
	public static void copy (int[] src, int srcOffset, Buffer dst, int numElements) {		
		copyJni(src, srcOffset << 2, dst, positionInBytes(dst), numElements << 2);
		dst.limit(dst.position() + bytesToElements(dst, numElements << 2));
	}
	
	/**
	 * Copies the contents of src to dst, starting from src[srcOffset], copying numElements
	 * elements. The {@link Buffer} instance's {@link Buffer#position()} is used to define
	 * the offset into the Buffer itself. The position will stay the same, the limit will be
	 * set to position + numElements. <b>The Buffer must be a direct Buffer with native byte order.
	 * No error checking is performed</b>.
	 * 
	 * @param src the source array.
	 * @param srcOffset the offset into the source array.
	 * @param dst the destination Buffer, its position is used as an offset.
	 * @param numElements the number of elements to copy.
	 */
	public static void copy (long[] src, int srcOffset, Buffer dst, int numElements) {		
		copyJni(src, srcOffset << 3, dst, positionInBytes(dst), numElements << 3);
		dst.limit(dst.position() + bytesToElements(dst, numElements << 3));
	}
	
	/**
	 * Copies the contents of src to dst, starting from src[srcOffset], copying numElements
	 * elements. The {@link Buffer} instance's {@link Buffer#position()} is used to define
	 * the offset into the Buffer itself. The position will stay the same, the limit will be
	 * set to position + numElements. <b>The Buffer must be a direct Buffer with native byte order.
	 * No error checking is performed</b>.
	 * 
	 * @param src the source array.
	 * @param srcOffset the offset into the source array.
	 * @param dst the destination Buffer, its position is used as an offset.
	 * @param numElements the number of elements to copy.
	 */
	public static void copy (float[] src, int srcOffset, Buffer dst, int numElements) {		
		copyJni(src, srcOffset << 2, dst, positionInBytes(dst), numElements << 2);
		dst.limit(dst.position() + bytesToElements(dst, numElements << 2));
	}
	
	/**
	 * Copies the contents of src to dst, starting from src[srcOffset], copying numElements
	 * elements. The {@link Buffer} instance's {@link Buffer#position()} is used to define
	 * the offset into the Buffer itself. The position will stay the same, the limit will be
	 * set to position + numElements. <b>The Buffer must be a direct Buffer with native byte order.
	 * No error checking is performed</b>.
	 * 
	 * @param src the source array.
	 * @param srcOffset the offset into the source array.
	 * @param dst the destination Buffer, its position is used as an offset.
	 * @param numElements the number of elements to copy.
	 */
	public static void copy (double[] src, int srcOffset, Buffer dst, int numElements) {		
		copyJni(src, srcOffset << 3, dst, positionInBytes(dst), numElements << 3);
		dst.limit(dst.position() + bytesToElements(dst, numElements << 3));
	}
	
	/**
	 * Copies the contents of src to dst, starting from the current position of src, copying
	 * numElements elements (using the data type of src, no matter the datatype of dst). The
	 * dst {@link Buffer#position()} is used as the writing offset. The position of both Buffers
	 * will stay the same. The limit of the src Buffer will stay the same. The limit of the dst Buffer
	 * will be set to dst.position() + numElements, where numElements are translated to the number of
	 * elements appropriate for the dst Buffer data type. <b>The Buffers must be  direct Buffers with native byte order.
	 * No error checking is performed</b>.
	 * 
	 * @param src the source Buffer.
	 * @param dst the destination Buffer.
	 * @param numElements the number of elements to copy.
	 */
	public static void copy(Buffer src, Buffer dst, int numElements) {
		int numBytes = elementsToBytes(src, numElements);
		copyJni(src, positionInBytes(src), dst, positionInBytes(dst), numBytes);
		dst.limit(dst.position() + bytesToElements(dst, numBytes));
	}
	
	private static int positionInBytes(Buffer dst) {
		if(dst instanceof ByteBuffer) return dst.position();
		else if(dst instanceof ShortBuffer) return dst.position() << 1;
		else if(dst instanceof CharBuffer) return dst.position() << 1;
		else if(dst instanceof IntBuffer) return dst.position() << 2;
		else if(dst instanceof LongBuffer) return dst.position() << 3;
		else if(dst instanceof FloatBuffer) return dst.position() << 2;
		else if(dst instanceof DoubleBuffer) return dst.position() << 3;
		else throw new GdxRuntimeException("Can't copy to a " + dst.getClass().getName() + " instance");
	}	
	
	private static int bytesToElements(Buffer dst, int bytes) {
		if(dst instanceof ByteBuffer) return bytes;
		else if(dst instanceof ShortBuffer) return bytes >>> 1;
		else if(dst instanceof CharBuffer) return bytes >>> 1;
		else if(dst instanceof IntBuffer) return bytes >>> 2;
		else if(dst instanceof LongBuffer) return bytes >>> 3;
		else if(dst instanceof FloatBuffer) return bytes >>> 2;
		else if(dst instanceof DoubleBuffer) return bytes >>> 3;
		else throw new GdxRuntimeException("Can't copy to a " + dst.getClass().getName() + " instance");		
	}
	
	private static int elementsToBytes(Buffer dst, int elements) {
		if(dst instanceof ByteBuffer) return elements;
		else if(dst instanceof ShortBuffer) return elements << 1;
		else if(dst instanceof CharBuffer) return elements << 1;
		else if(dst instanceof IntBuffer) return elements << 2;
		else if(dst instanceof LongBuffer) return elements << 3;
		else if(dst instanceof FloatBuffer) return elements << 2;
		else if(dst instanceof DoubleBuffer) return elements << 3;
		else throw new GdxRuntimeException("Can't copy to a " + dst.getClass().getName() + " instance");		
	}
	
	private native static void copyJni (float[] src, Buffer dst, int numFloats, int offset) /*-{ }-*/;
	private native static void copyJni (byte[] src, int srcOffset, Buffer dst, int dstOffset, int numBytes) /*-{ }-*/;
	private native static void copyJni (char[] src, int srcOffset, Buffer dst, int dstOffset, int numBytes) /*-{ }-*/;
	private native static void copyJni (short[] src, int srcOffset, Buffer dst, int dstOffset, int numBytes) /*-{ }-*/;
	private native static void copyJni (int[] src, int srcOffset, Buffer dst, int dstOffset, int numBytes) /*-{ }-*/;
	private native static void copyJni (long[] src, int srcOffset, Buffer dst, int dstOffset, int numBytes) /*-{ }-*/;
	private native static void copyJni (float[] src, int srcOffset, Buffer dst, int dstOffset, int numBytes) /*-{ }-*/;
	private native static void copyJni (double[] src, int srcOffset, Buffer dst, int dstOffset, int numBytes) /*-{ }-*/;
	private native static void copyJni (Buffer src, int srcOffset, Buffer dst, int dstOffset, int numBytes) /*-{ }-*/;

	public static FloatBuffer newFloatBuffer (int numFloats) {
		ByteBuffer buffer = ByteBuffer.allocateDirect(numFloats * 4);
		buffer.order(ByteOrder.nativeOrder());
		return buffer.asFloatBuffer();
	}
	
	public static DoubleBuffer newDoubleBuffer (int numDoubles) {
		ByteBuffer buffer = ByteBuffer.allocateDirect(numDoubles * 8);
		buffer.order(ByteOrder.nativeOrder());
		return buffer.asDoubleBuffer();
	}

	public static ByteBuffer newByteBuffer (int numBytes) {
		ByteBuffer buffer = ByteBuffer.allocateDirect(numBytes);
		buffer.order(ByteOrder.nativeOrder());
		return buffer;
	}
	
	public static ShortBuffer newShortBuffer (int numShorts) {
		ByteBuffer buffer = ByteBuffer.allocateDirect(numShorts * 2);
		buffer.order(ByteOrder.nativeOrder());
		return buffer.asShortBuffer();
	}
	
	public static CharBuffer newCharBuffer(int numChars) {
		ByteBuffer buffer = ByteBuffer.allocateDirect(numChars * 2);
		buffer.order(ByteOrder.nativeOrder());
		return buffer.asCharBuffer();
	}

	public static IntBuffer newIntBuffer (int numInts) {
		ByteBuffer buffer = ByteBuffer.allocateDirect(numInts * 4);
		buffer.order(ByteOrder.nativeOrder());
		return buffer.asIntBuffer();
	}
	
	public static LongBuffer newLongBuffer (int numLongs) {
		ByteBuffer buffer = ByteBuffer.allocateDirect(numLongs * 8);
		buffer.order(ByteOrder.nativeOrder());
		return buffer.asLongBuffer();
	}

	/**
	 * Writes the specified number of zeros to the buffer. This is generally faster than reallocating a new buffer.
	 */
	public static native void clear (ByteBuffer buffer, int numBytes);
}
